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A107373 (n/2)*binomial(n-1,floor((n-1)/2)) - 2^(n-2). 3
0, 0, 1, 2, 7, 14, 38, 76, 187, 374, 874, 1748, 3958, 7916, 17548, 35096, 76627, 153254, 330818, 661636, 1415650, 2831300, 6015316, 12030632, 25413342, 50826684, 106853668, 213707336, 447472972, 894945944, 1867450648, 3734901296, 7770342787, 15540685574 (list; graph; refs; listen; history; text; internal format)
OFFSET

1,4

LINKS

Vincenzo Librandi, Table of n, a(n) for n = 1..1000

Igor Pak, The area of cyclic polygons: Recent progress on Robbins' Conjectures, Adv. Applied Math. 34 (2005), 690-696. Special issue in memory of David Robbins.

F. Disanto and S. Rinaldi, Symmetric convex permutominoes and involutions, PU. M. A. 22:1 (2011), 39-60.

FORMULA

a(2n) = 2*A000531(n-1); a(2n+1) = A000531(n). - Max Alekseyev, Sep 30 2013

(1-n)*a(n) +2*(n-1)*a(n-1) +4*(n-2)*a(n-2) +8*(-n+2)*a(n-3)=0. - R. J. Mathar, May 26 2013

MAPLE

A056040 := n -> n!/iquo(n, 2)!^2:

A133265 := n -> (n+2+(n-2)*(-1)^n)/2:

A107373 := n -> (A056040(n)*A133265(n)-2^n)/4:

seq(A107373(n), n=1..34); # Peter Luschny, Aug 30 2011

MATHEMATICA

Table[(n/2) Binomial[n-1, Floor[(n-1)/2]] - 2^(n-2), {n, 1, 40}] (* Vincenzo Librandi, Oct 01 2013 *)

PROG

(MAGMA) [(n/2)*Binomial(n-1, Floor((n-1)/2)) - 2^(n-2): n in [1..40]]; // Vincenzo Librandi, Oct 01 2013

CROSSREFS

Cf. A131019-A131021.

Sequence in context: A018497 A178748 A194590 * A176662 A018526 A018542

Adjacent sequences:  A107370 A107371 A107372 * A107374 A107375 A107376

KEYWORD

nonn

AUTHOR

N. J. A. Sloane, Jul 20 2007

STATUS

approved

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Last modified March 24 11:49 EDT 2019. Contains 321448 sequences. (Running on oeis4.)